Many thanks for the info, I'm slowly building the engine and it has a GB gear cluster in it so is wide ratio, I would mainly use the bike for pre 65 trials, it would be nice to do the odd classic road trial but will be mainly trials sections. I'm waiting for the frame at the minute so I will have to wait for chain clearance measurements. I have cub hubs front and rear and have just got them back from the powder-coating after making the rear hub 35mm wider. I will get the 18T primary sprocket and seal, it would be nice to fit the drive sprocket and build up the clutch basket etc.